To sea or not to see

I have spent the best part if the last two days diving in and out of very low visibility water. Visibility has been so low that I can't even see my hand in front of my face as I dive to the sea floor. It has been interesting to hear from more experienced divers how they feel about the low visibility. As they are used to diving in clear water, they find it rather disconcerting diving in the muddy, turbid water of Moreton Bay. Because I don't know any different, I launch into the water, swim blindly to the bottom and grab whatever it is I can find.

Three of us have been doing the diving off 'Tender', the little boat that skips across the surface at a rate of about 30km. Every tiny wave it hits means that all on board get a drenching. In 2 days we did about 175 dives! Yes, we hit mud a lot of the time (in the space of 20 dives yesterday I only hit seagrass 2 times and even then it was very sparse coverage).

dive     massofseagrass

             Diving for seagrass off the small boat (Tender)                    Seagrass collected over the course of a few dives 

 

We went to the southern bay to see how far south the seagrass was distrubuted. We would pull up alongside some mangroves, dive in, grab hold of a rope attached to the front of the boat and then get towed to the next stop. This was much quicker than constantly jumping in and out of water.

What we found was mostly mud. This mud has formed from the sediment that has been washed down the Logan River and deposited in the bay. This sediment is mainly from urban development and argiculture that is washed in the river when it rains. A classic example of how the upper catchment of a river system affects the bay. Seagrass need certain light conditions in order to live so struggle if the water is too turbid (i.e. muddy). Apparently there used to be a lot of seagrass in this area - but alas, no more.

In the evenings I have been assisting with data entry. We type in the latitude and longitude, seagrass coverage, depth and sediment type into a spreadsheet. This data is then synched with Power BI (a data visualisation site) in order to show a map of the dive sites as well as graphs and charts of seagrass coverage. The images below show the raw data and then a snapshot of the GPS points after they have been mapped (thanks to intern Mitch for letting me help with data entry).

rawdata             gpspoints