Reef station at Mar del Sur logs warmest water on record

The Costa Mar Reef Monitoring Network's southern station at Mar del Sur recorded its warmest surface water temperature since the network began keeping records in 2009, logging 29.8°C at 06:00 local time on Thursday. The reading surpasses the previous peak of 29.4°C set in September 2023 and marks the eleventh consecutive week that the station has exceeded the seasonal average.

The measurement comes from the network's buoy number four, anchored two kilometres off the Mar del Sur headland, where the reef shelf drops sharply into deeper water. Network coordinator Elena Vasquez said the sustained warmth is no longer an anomaly but a pattern that the region's monitoring stations have been tracking with growing concern since early June.

Marine biologists at the station have begun daily visual inspections of the staghorn coral thickets in the shallow lagoon, looking for the first signs of the paling that precedes bleaching. The network's bleaching alert protocol, last activated in 2023, has been raised to its second-highest level, though no widespread bleaching has yet been confirmed.

The warm water has also drawn the attention of the Federal Hydro Authority, which manages the region's hydroelectric grid and has been monitoring ocean temperatures for their effect on coastal weather patterns. What the next weeks bring will depend on the behaviour of the seasonal current that usually cools the southern reef in August.