Tag Archives: quadrat

Day 11: Counting corals and urchins

The projects of the day consisted of comparing live stony coral cover and numbers of urchins between the Marine Protected Area (MPA) and a zone outside of the MPA at Glovers Reef. To measure coral cover, we laid down 7 transects that were each 100 ft long. Every 25 ft along the transect we measured two quadrats that were 2 ft by 2 ft. Each quadrat is fitted with twine to make 81 squares, or 64 intersection points. We looked at what was underneath each intersection and classified it as live stony coral, recently dead stony coral, macroalgae, other living organisms, or other dead/abiotic objects. Tomorrow we will analyze the data that we gathered, but we predicted that there would be a higher percent of live coral cover inside the MPA.

To count urchins, we timed how many urchins 18 people could collect in 25 minutes. Tomorrow we will compile all of the data and determine which urchin species were most common and quantify the difference between the MPA and the area outside the MPA.

Collected urchins (Photo credit: Scott)
Collected urchins (Photo credit: Scott)

We didn’t have very much time to explore the reef, but during data collection I was able to observe several species of parrotfish, including what I believe was a stoplight parrotfish. I also noted a large number of flamingo tongue snails, which are an interesting species of mollusk that is mostly an off-white shade with yellow spots that have a black outline. The snails are mostly found on sea fans.

As for green algae, I saw pinecone algae in the MPA. The pinecone algae are concentrated in sandy areas where they are able to attach their holdfast to the sand. The pinecone algae were smaller than I was expecting and were narrower, so they could be a slightly different species than I researched. There was also calcareous green algae that was growing on dead coral both in the MPA and outside of it. While the algae consisted of multiple species, I believe that most of them were species of Halimeda. Most of the green algae that I saw today was covered in sediment so it was difficult to identify the exact species.

Day 10: Quadrats and Transects

We started off this morning with a refreshing snorkel session at 8:30am. This time we brought out more gear, specifically a clipboard with waterproof paper to take notes of what we saw. There was a general feeling among all of us that the waterproof paper had to be some sort of black magic, but it worked so we stopped questioning it. Holding the clipboard and trying to take photos and write notes while avoiding being pushed into the coral by the currents took a long time to get used to, and I definitely haven’t mastered it.

DSCN1263
Gathering data in sea grass beds

To make everything more confusing, we added more gear after lunch. We performed a short experiment to practice using transect tapes and quadrats. The question that we were trying to answer was whether Halimeda or Penicillus species had a higher abundance and density in the sea grass off of the pier at Middle Caye. We worked in 6 groups to run transects across the beds of sea grass and counted the number of individuals of each species in quadrats along the transects.

In the end, we found 153 Halimeda individuals and only 1 Penicillus individual in the 216 square feet that we measured. We noticed that even slight differences in the composition of the sea grass bed, such as the density or length of the grass, changed the likelihood of algae being found in the plot. To quantify these differences we would have to run another experiment that focused on the different zones in the sea grass bed. Our experiment was limited because of the small area that we covered and difficulty that we had counting the individuals. Even though we were in water that was 8 feet deep at most, it might have been easier to run the experiment using SCUBA so we wouldn’t have to keep surfacing, which made counting confusing when we had to see under blades of grass.

Halimeda and Penicillus are interesting green algae because they are calcareous. Halimeda incorporates calcium carbonate into its thallus in flat chips, whereas Penicillus has calcium carbonate in the brush-like filaments at the top of the algae. The different forms of calcium carbonate lead to different types of sand. Halimeda creates large, flat grains of sand. The sand from Penicillus is finer and muddier.

Day 10

Today was our first complete day on the reef. I can’t really put into words how lovely it is here. Sure I have sand on just about every surface of my body, but I am thoroughly enjoying my time here. The day was centered on two tools: the transect and quadrat.

First, we tried to quantify the percent cover of crab holes on the paths around the station (using the quadrats/transect on land). Honestly, my group did not get that much data (only one half of a square was covered over our entire transect).

This was then scaled up for our afternoon activity, transects searching for two geneses of green algae (Halimeda and Penicillus). We were trying to answer a similar question to the percent crab hole cover. We wanted to know if Halimeda or Penicillus would be more abundant in the sea grass bed.

Again, my groups struggled to find anything on our transect, with it being placed in some of the thickest grass. Either way, our data showed a significantly higher amount of Halimeda over Penicillus.

On the reef I continued to see Gorgonian sea fans, as well as whips and rods. I think that the future challenge that I will face is distinguishing between soft corals that are branching, yellow/brown, with them all being of similar morphology. Tomorrow on the more distant reef, I hope to see more.