After a few days of delayed luggage and missing equipment, we were finally reunited with our bags and could start off our research.
We took this opportunity whilst on the move to investigate the red tide that we were sailing through. During a red tide the sea will appear a dark red or brown colour, due to the presence of phytoplankton, in this case Trichodesmium spp. They bloom off the west coast of Costa Rica where riverine runoff supplies high levels of nutrients from local plantations. This is known as eutrophication. The plankton utilise the nutrients creating high productivity till a bloom occurs.
However, during this process oxygen in the water is utilised and creates hypoxic environments. This disrupts the ecosystem as it makes it uninhabitable for many other organisms that would usually prevail. We used the microscopes on board to identify the species present and unsurprisingly Trichodesmium dominated the sample with low species diversity. Sadly within this small sample we identified a piece of micro-plastic.
During our sails we have seen many plastic debris especially within this location of sampling. In this inlet, water masses meet and thus traps debris within the current. It is likely that the plastic debris and eutrophication are coming from the same source - the rivers.