On the 17th March 2007, our group met up with people from teamseagrass for our second recce at Labrador Park. This time, we were going to test and find out which method to check for seagrass population density in specific areas would be the most effective.
Usually for monitoring, a horizontal transect line is laid out for 50m, and a vertical one which starts at the start point of the horizontal transect line is laid out for another 50m. GPS readings are taken at the start and end points of the transect lines, so we can find the same spot again on another day. A quadrat (a square-shaped border made of pipes, which have holes drilled into them and string passing through, holes, and basically looks something like a square grid) is then laid out at every 5m on the vertical scale. Based on a data sheet for the seagrass percent cover standards, we can estimate the percentage (amount) of seagrass there is in each quadrat.
The methods that we were considering were the random band method, 100m by 25m, or 50m by 50m. The random band method involves laying out transect lines as well, but instead of laying down quadrats at every 5m, the quadrats are thrown randomly around areas where there are seagrass patches. We decided not to use it, for it might leave us with skewed data. Instead, we debated over whether the 100m by 25m, or the 50m by 50 would be more feasible, but our questions were resolved when we laid out the transect lines. The seagrass patch mostly ended around the 50m mark, so it would not be very feasible to lay out the transects until the 100m mark.
Using the surroundings to help us benchmark the area, e.g. a pillar for the 25m mark, we made it easier to identify the area if there was a need to. At every 5m, we also took down notes of what was in the surrounding area, for example, rocks, halophila ovalis, colonial anemone, etc. This would help us to identify what were the factors that affected the presence of seagrass in the area.
Along the way, we had a lot of fun studying the many marine creatures that we saw and learning what they were called. For example, we saw the colourful Velcro crab, which covered itself with different types of algae as a form of camouflage, making it more difficult to spot. We also spotted other things like a nudibranch (a sea slug- the spotty green thing in the picture),
a red egg crab, hairy crab, and more! We eagerly look forward to our next session at Labrador Park! (:
click here for the TeamSeagrass post on the recce with nice photos!
Labels: monitoring methods, recce, Team Seagrass