Mass coral bleaching at Saipan lagoon

Federal surveys reinforce status of imperiled coral, sea life in lagoon
Dennis B. Chan Saipan Tribune 21 Aug 16;

The Bureau of Environmental Quality on Friday concurred with recent survey observations from federal biologists revealing wide spread coral death in the Saipan lagoon and ongoing coral bleaching.

The local environmental agency points to warming sea surface temperatures as the likely causes.

This month, National Oceanic and Atmospheric Administration marine ecologists Matt Kendall and Bryan Costa completed a two-week survey on the Saipan lagoon, covering about 550 dive spots where they recorded high resolution video and observed the state of coral, sea grass, and bottom life there.

Kendall says that most of the staghorn coral they saw were dead.

“Ninety percent of it, especially, in the Wing Beach and Sugar Dock area is dead. And the 10 percent that is left, is bleached.”

“That’s not good,” he added. This means if bleaching is severe, the coral will probably die. And if the bleaching does not kill the coral, a burst of disease usually hits a few months after bleaching occurs.

“That kills a lot of coral too, if the bleaching doesn’t do it,” Kendall said in a recent interview.

On Friday, BECQ said bleaching events in 2013 and 2014 caused the majority of the death.

BECQ lead biologist Lyza Johnston said these events as well as the current bleaching are due to “warmer than usual sea surface temperatures.”

She added, though, that other local stressors like polluted runoff, physical damage (anchors, stepping on the corals), sedimentation, and overfishing can reduce the resilience of the corals—making them more susceptible to broader scale disturbances like bleaching from thermal stress.

“So we need to try to reduce or eliminate as many of the stressors as possible to keep the reefs healthy so they have a chance to bounce back from disturbances,” Johnston said in an email to Saipan Tribune.

Johnston said BECQ has also observed the same patterns as the NOAA biologists.

After the 2013/14 bleaching, she said, BECQ recorded a loss of 85 percent of staghorn corals at their long-term monitoring sites in the lagoon.

The agency, she said, will be going out in the next few weeks to assess the current bleaching, which seems to be restricted to the lagoon at this point.

“These [recent] storms and cloudy weather have actually been really good for the coral as it has caused a drop in water temperatures and sunlight. So hopefully it won’t be as bad as was predicted earlier in the summer when we thought we would start seeing widespread bleaching by the end of August.”

Habitat harmed

Kendall said that even the coral survives the bleaching and disease, they may not grow or reproduce as fast.

For the 90 percent of dead staghorn seen, Kendall says there are still standing coral, and not broken down into rubble yet.

“What happen is, sponges and other organism burrow in there, algae puts in little roots, organism bore into it to make their homes, waves come along and break that coral skeleton and you still have these complex thicket of branches where fish and other organism like to live—all of it breaks down and gets flat. And that’s a total different habitat that is not great for a lot of the fish that need to hide in those branching areas of the coral,” Kendall said.

Kendall also said they were surprised to find large swaths of cyanobacteria in the lagoon, where otherwise they expected plain sand.

The NOAA biologists drew on maps from biologist Peter Houk some 10 years ago for their initial drafts of the lagoon.

They hope to finish their high resolution mapping replete with depth and other features by the end of the year, to make it public by early next year.

The previous maps, for one, did not show large swaths of algae that the biologists say covered a large area in the lagoon.

“We swam down there and it was this algal mat…It covered huge areas. It’s not a good thing. It’s a sign of too much nutrients in the water. It’s a sign that something is not right. What it tends to do is kind of smother everything and does not leave enough room [for life] to grow,” Kendall said.

‘Lagoon use mapping plan’

All the recently recorded data will go toward helping BECQ’s “lagoon use mapping plan.”

Big picture in mind, BECQ and NOAA are working really closely to understand “what’s out there and how it’s changed” since the last time the lagoon was mapped some 10 years ago, Kendall said.
The biologists aim to get more spatially resolved maps, or extremely detailed and precise maps of the lagoon’s bottom.

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